1
Q
SN2 vs E2 Substrate Selectivity
A
- SN2 Favorable:
Me > primary > secondary (sterics) - E2 Favorable:
teritary > secondary > primary (more anti-bonding C-H’s - less anti-coplanar C-H a d C-LG: less E2 more SN2
2
Q
SN2 vs E2: Nucleophile/Base
A
- SN2: better nucleophile (smaller/polarizable)
- E2: better Bronsted base (bulky/highly basic)
- strong, bulky bases favor E2 over SN2 (hindered strong bases make poor nucleophiles!)
3
Q
SN2 vs E2: Temperature
A
- E2: HIGH TEMP FAVORED (greater chance in entropy)
4
Q
SN1 vs E1 Substrate Selectivity
A
- SN1: tertiary or resonance
- E1: tertiary or resonance
5
Q
SN1 vs E1: Nu/Base
A
- SN1: no effect on rate
- E1: no effect on rate
- weak bases ok!!!
6
Q
SN1 vs E1: Temperature
A
- E1 favored at high temperatures!
7
Q
Generally which is preferred? E1 or E2?
A
- Difficult to influence SN1 over E2 (use strong base to favor elimination by E2)
8
Q
Best Conditions: SN1 Primary
A
- NOPE
9
Q
Best Conditions: SN1 Secondary and Tertiary
A
- weak Nu
- protic Solvent
- lower T
10
Q
Best Conditions: E1 Primary
A
- NOPE
11
Q
Best Conditions: E1 Secondary and Tertiary
A
- weak Nu
- protic Solvent
- higher T
12
Q
Best Conditions: SN2 Primary
A
- unhindered Nu
- aprotic solvent
- low T
13
Q
Best Conditions: SN2 Secondary
A
- strong unhindered Nu
- aprotic solvent
- low T
14
Q
Best Conditions: E2 primary
A
- bulky base
- aprotic solvent
- higher T
15
Q
Best Conditions: E2 secondary
A
- bulky strong base
- aprotic solvent
- higher T
16
Q
Best Conditions: SN2 Tertiary
A
- NOPE
17
Q
Best Conditions: E2 Tertiary
A
- Strong base
- aprotic solvent
- high T
18
Q
Method to the Method
A
- Is there a suitable leaving group?
- What kind of carbon is bonded to the leaving group?
- Examine Nu/Base strength/Concentration and solvent
- If E1/SN1 or E2/SN2 equally likely, consider temp.
CHEM212
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